Call special VM interpolate for single element interpolation.

runtime/vm/intermediate_language.h

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_INTERMEDIATE_LANGUAGE_H_
 #define VM_INTERMEDIATE_LANGUAGE_H_
 
 #include "vm/allocation.h"
 #include "vm/ast.h"
 #include "vm/growable_array.h"
@@ skipping 3782 matching lines @@
 
  private:
   const intptr_t cid_;
 
   DISALLOW_COPY_AND_ASSIGN(StringToCharCodeInstr);
 };
 
 
 class StringInterpolateInstr : public TemplateDefinition<1> {
  public:
-  StringInterpolateInstr(Value* value, intptr_t token_pos)
-      : token_pos_(token_pos), function_(Function::Handle()) {
+  StringInterpolateInstr(Value* value, intptr_t token_pos, bool is_singleton)
+      : token_pos_(token_pos),
+        function_(Function::Handle()),
+        is_singleton_(is_singleton) {
     SetInputAt(0, value);
   }
 
   Value* value() const { return inputs_[0]; }
   virtual intptr_t token_pos() const { return token_pos_; }
 
   virtual CompileType ComputeType() const;
   // Issues a static call to Dart code which calls toString on objects.
   virtual EffectSet Effects() const { return EffectSet::All(); }
   virtual bool CanDeoptimize() const { return true; }
   virtual bool MayThrow() const { return true; }
 
   const Function& CallFunction() const;
 
   virtual Definition* Canonicalize(FlowGraph* flow_graph);
 
   DECLARE_INSTRUCTION(StringInterpolate)
 
  private:
   const intptr_t token_pos_;
   Function& function_;
+  const bool is_singleton_;
 
   DISALLOW_COPY_AND_ASSIGN(StringInterpolateInstr);
 };
 
 
 class StoreIndexedInstr : public TemplateDefinition<3> {
  public:
   StoreIndexedInstr(Value* array,
                     Value* index,
                     Value* value,
@@ skipping 4614 matching lines @@
       Isolate* isolate, bool opt) const {                                     \
     UNIMPLEMENTED();                                                          \
     return NULL;                                                              \
   }                                                                           \
   void Name::EmitNativeCode(FlowGraphCompiler* compiler) { UNIMPLEMENTED(); }
 
 
 }  // namespace dart
 
 #endif  // VM_INTERMEDIATE_LANGUAGE_H_